Brown Noise Generator
Play deep, endless brown noise that never loops or stops on its own. Make it warmer or brighter, wider or mono, fade it in gently and let the sleep timer fade it out while you drift off. It keeps playing when you switch tabs.
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How to use the Brown Noise Generator
- Press Play brown noise. The sound fades in over the time chosen under Fade-in.
- Pick a preset such as Deep sleep or Focus, or adjust Volume yourself.
- Shape the sound with Warmth (move right for a darker, softer rumble) and Stereo width.
- Set the sleep timer and fade-out length if you want it to stop on its own.
- Switch tabs freely: the noise keeps playing in the background until you press Stop or the timer ends.
- Optional: press Download WAV loop to save a seamless loop for a speaker or phone.
Noise colours compared
Noise "colours" describe how the power of random noise is spread across frequencies. Each step from white to pink to brown tilts the spectrum further towards the bass by 3 dB per octave.
| Noise | Power spectrum | Slope per octave | Sounds like | Typical use |
|---|---|---|---|---|
| White | Flat (constant) | 0 dB | Hiss, TV static | Masking speech, audio testing |
| Pink | ∝ 1/f | −3 dB | Steady rain | Sleep, speaker calibration |
| Brown (red) | ∝ 1/f² | −6 dB | Waterfall, strong wind, distant thunder | Sleep, focus, masking low hum |
Because brown noise loses 6 dB per octave, a 1,000 Hz band carries about 1/100 of the power of a 100 Hz band (20 dB less). Each time frequency doubles the power drops to a quarter, which is why it sounds so smooth and bassy.
How to choose the warmth and stereo settings
- Warmth adds a low-pass filter on top of the natural brown slope. Around 500 to 1,000 Hz sounds like a classic brown noise; 200 Hz and below becomes a soft, distant rumble with almost no hiss.
- Small speakers and phones can't reproduce deep bass, so very warm settings may sound quiet. Move Warmth to the left or raise the volume a little.
- Headphones: a stereo width of 60 to 100% sounds natural and spacious. Use 0% (mono) with a single earbud so you don't miss half of the sound.
- Keep it quiet: masking works at a low volume. If you can't comfortably talk over it, it is louder than it needs to be.
Sleep timer and background playback
The timer is scheduled directly on the Web Audio clock rather than with a page timer, so the fade-out starts on time even when the tab sits in the background for hours. The fade is a smooth volume ramp over the length you choose, after which the audio engine is suspended to save battery. If you change the timer while the noise is playing, it restarts from that moment.
Frequently asked questions
What is brown noise?
Brown noise (also called red or Brownian noise) is random noise whose power falls by 6 dB for every doubling of frequency, so its power spectrum is proportional to 1/f². Compared with white noise it has much more bass and much less hiss, which is why it sounds like a deep rumble, a waterfall or wind. The name comes from Brownian motion, not from the colour.
How is the brown noise generated here?
Each channel adds a small random value to the previous sample (b = 0.997 × b + 0.02 × white), which is a leaky integration of white noise. Integration produces the 1/f² spectrum; the slight leak and a 20 Hz high-pass filter stop the signal from drifting. The generator runs live in an AudioWorklet, so the sound never repeats.
Brown noise vs white noise vs pink noise: what is the difference?
White noise has equal power at every frequency and sounds like hiss. Pink noise falls 3 dB per octave (power ~1/f) and sounds like steady rain. Brown noise falls 6 dB per octave (power ~1/f²) and sounds deepest and softest. Many people find brown noise the least tiring for long listening because it has the least high-frequency energy.
Will it keep playing if I switch tabs or the screen dims?
On desktop browsers yes: the noise is generated in the audio thread and the sleep timer is scheduled on the audio clock, so neither is affected by background-tab throttling. Phones may pause web audio when the screen locks or the browser goes to the background; if that happens, keep the page open in the foreground or download the WAV loop and play it in a music app on repeat.
Is brown noise safe for babies?
Keep the volume low and the speaker well away from the cot. A 2014 study in the journal Pediatrics found that some infant sleep machines can exceed recommended noise limits at maximum volume, and the authors advised placing them as far from the crib as possible, at a low volume and for a limited time. The sleep timer and fade-out help with that.
Does brown noise help with focus or ADHD?
Many people report that steady background noise masks distracting sounds and helps them concentrate, and brown noise has become popular for this. Research on noise and attention is limited and results vary from person to person, so treat it as a comfort tool and try different warmth and volume settings to see what works for you.
What does the stereo width slider do?
At 100% the left and right ears get two independent noise signals, which sounds wide and spacious. At 0% both ears get the same signal (mono), which is better for a single earbud or a mono speaker. The level is compensated so the loudness stays the same as you change the width.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.